Same here. I turned off geforce experience and still get a black screen that then collapses to the task bar.
I'm going to try to roll back to the previous patch via galaxy and try to re-patch.

I had the same problem. A completely fresh installation solved the problem for me.
So at first I uninstalled all dlcs and the base game. After this I installed the base game again and following this, I patched it with the new patch 1.10. In the end I installed the all the dlcs again with the new installer.

I was hoping I can avoid reinstalling the game but well.
I rolled back to patch 8 and game was running OK.
Still I see there is a lot of performance issues with the latest patch so I'll just wait for some hotfix if not I'll reinstall the game...

Looks like I'll have to try that as nothing else has worked. I've backed up my saves but am wondering whether to start from scratch.
Good to hear this fixes it though :-)

Update and solution for anyone else who might have this problem.

I deleted and re-installed the Witcher 3 and it ran fine until I loaded the Nvidia (geforce experience) game optimizations, at which point it did the black screen behavior. Reverting to its un-optimized state allowed it to run perfectly. It looks like the Geforce settings can't cope with the latest patch.